Steady-state theory

A cosmological model in which the universe expands while continuous matter creation keeps its average density constant. It holds that the universe has no beginning or end and looks broadly the same at all times.

Perfect cosmological principle: The principle that the universe looks the same at every place and every time, on large scales. Steady-state theory extends the usual large-scale uniformity principle to time.
Fred Hoyle: A British astronomer who developed steady-state cosmology and coined the term “Big Bang.” Hoyle formulated the theory and later revised it with collaborators.
Cosmic microwave background: Diffuse microwave radiation that fills the universe, interpreted as relic radiation from its hot early phase. Its measured spectrum and origin strongly favored a hot early universe over classical steady state.
Lambda-CDM model: The standard cosmological model combining cold dark matter with a cosmological constant in an expanding universe. It explains cosmic expansion and observations without continuous creation maintaining constant density.
Hubble–Lemaître law: The relationship between a galaxy's distance and its recession speed, indicating cosmic expansion. Expansion would dilute matter unless steady-state theory replenished it.
Hermann Bondi: An Austrian-British mathematician and cosmologist who helped develop steady-state cosmology. Bondi helped establish the theory's principles and mathematical framework.
Radio source counts: Statistical measurements of how many radio-emitting astronomical sources occur at different observed strengths. Source counts indicated cosmic populations changed over time, challenging steady-state predictions.
Evolving universe: A universe whose large-scale properties change over cosmic time. Steady-state theory rejects cosmic evolution in favor of an unchanging large-scale appearance.
C-field: A field introduced in steady-state cosmology to represent the creation of matter. Hoyle's formulation used this field to sustain density as space expanded.
Thomas Gold: An Austrian-American astrophysicist who co-founded steady-state cosmology with Bondi and Hoyle. Gold proposed the model alongside Bondi and Hoyle in 1948.

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